Led characterization and compensation methods and systems

Abstract

Systems and methods for monitoring, characterizing and controlling operation of LEDs are provided herein. Methods includes measuring a voltage across the LED, and correlating the voltage to a junction temperature of the LED. This correlation can be used to improve operation of the LED by increasing the signal to noise ratio of the LED signal, characterize the LED by comparing to an I-V curve, control LED operation to compensate for LED degradation and avoid crosstalk, and/or to generally improve performance and life expectancy of the LED. Improved performance of the LED can include stabilizing the photon output during performance of an assay to provide a desired dye reporter signal required for the assay and/or reducing an intra-shot during of the LED output during the assay. System and device with control units configured to perform these methods are also described herein.

1 . A diagnostic assay instrument comprising:
 a light-emitting diode (LED) configured to provide an optical output for excitation of a biological sample received within the instrument to monitor performance of an assay;   an optical detector configured to detect reactions in the sample in response to optical excitation within the assay; and   a control unit having a processor and a voltage sensor, the control unit configured to operate the LED to monitor performance of the assay, wherein the processor includes instructions recorded thereon configured for:
 measuring a voltage across the LED to operate at a given current; and 
 correlating the voltage to a junction temperature of the LED such that the voltage is a proxy of the junction temperature. 
   
     
     
         2 . The instrument of  claim 1  wherein the control unit is further configured to:
 determine a characteristic and/or control the LED based on the measured voltage. 
 
     
     
         3 . The instrument of  claim 2  wherein the correlation is determined without any temperature sensor input. 
     
     
         4 . The instrument of  claim 2  wherein the characteristic of the LED is determined by obtaining an I-V curve during an output pulse of the LED and comparing to a reference I-V curve. 
     
     
         5 . The instrument of  claim 2  wherein the control unit is configured to determine the characteristic upon each start-up of the system. 
     
     
         6 . The instrument of  claim 2  wherein the control unit is configured to determine the performance characteristic during operation of the LED. 
     
     
         7 . The instrument of  claim 1  wherein the control unit is configured to use the measured voltage to reduce a noise-to-signal ratio of the LED signal. 
     
     
         8 . The instrument of  claim 1  wherein the control unit is configured such that the voltage across the LED is within a voltage range, wherein the control unit is further configured to:
 monitor the entire voltage range at a first resolution, and 
 monitor a sub-range at a second resolution higher than the first resolution. 
 
     
     
         9 . The instrument of  claim 8  wherein the second resolution is at least an order of magnitude higher than the first resolution. 
     
     
         10 . The instrument of  claim 8  the control unit includes is configured to increase resolution of the sub-range by amplifying the voltage signal within the sub-range. 
     
     
         11 . The instrument of  claim 8  the control unit is configured to increase resolution of the sub-range by:
 outputting a reference voltage in the sub-range and 
 comparing the reference voltage to the LED signal within the sub-range. 
 
     
     
         12 . The instrument of  claim 11  wherein the control unit is further configured to multiply a difference between the reference voltage and the voltage signal by a high gain, thereby increasing the resolution of the voltage measurement in the sub-range. 
     
     
         13 . A control unit for magnifying a voltage signal of an LED comprising:
 an LED configured to provide an optical output; and   a control unit having a processor and a voltage sensor, the control unit configured to operate the LED, wherein the processor includes instructions recorded thereon to measure a voltage across the LED over an operating voltage range for a given current;   wherein the control unit is further configured to:   measure the voltage range at a first resolution with a voltage sensor of the first resolution, and   measure the voltage range in a selected sub-range of the voltage range at a second resolution higher than the first resolution with the voltage sensor of the first resolution.   
     
     
         14 - 17 . (canceled) 
     
     
         18 . A method of monitoring an optical component of a diagnostic instrument, the method comprising:
 starting-up and/or operating an LED to provide a photonic output;   measuring, with a control unit operably coupled to the LED, a voltage across the LED operating at a given current; and   correlating the voltage to a junction temperature of the LED such that the voltage is a proxy of the junction temperature.   
     
     
         19 - 30 . (canceled) 
     
     
         31 . A method for magnifying a voltage signal of an LED:
 operating, with a control unit, an LED to emit an optical output, the LED having an operating voltage range when operating at a given current;   measuring, with the control unit, a voltage signal of the LED at a first resolution with a voltage sensor having a first resolution; and   measuring, with the control unit, the voltage signal of the LED in a selected sub-range of the operating voltage range at a second resolution that is higher than the first resolution with the voltage sensor of the first resolution.   
     
     
         32 - 35 . (canceled) 
     
     
         36 . A diagnostic instrument comprising:
 an LED configured to provide an optical output for excitation of a biological sample received within the instrument for an assay to detect a target analyte;   an optical detector configured to detect reactions in the sample in response to optical excitation to detect the target analyte; and   a control unit having a processor and a voltage sensor, the control unit configured to operate the LED to monitor performance of the assay, wherein the processor includes instructions recorded thereon configured for:
 measuring a voltage across the LED during operation at a given current; 
 correlating the voltage to a junction temperature of the LED such that the voltage is a proxy of the junction temperature; 
 determining fluctuations in the junction temperature of the LED in real-time; and 
 controlling operation of the LED based on the real-time determinations to compensate for fluctuations in photonic output of the LED due to changes in the junction temperature. 
   
     
     
         37 - 41 . (canceled) 
     
     
         42 . A method of operating an LED in a diagnostic instrument, the method comprising:
 operating, with a control unit, an LED of the diagnostic instrument, to provide an optical output for excitation of a biological sample received within the instrument for an assay to detect a target analyte;   operating, with the control unit, an optical detector to detect reactions in the sample in response to optical excitation to detect the target analyte;   measuring, with the control unit, a voltage across the LED during operation when operating at a given current;   correlating, with the control unit, the LED voltage to a junction temperature of the LED such that the voltage is a proxy of the junction temperature;
 determining, with the control unit, fluctuations in the junction temperature of the LED in real-time based on the correlation; and 
   controlling, with the control unit, operation of the LED based on the real-time determinations to compensate for fluctuations in photonic output of the LED due to changes in the junction temperature of the LED.   
     
     
         43 - 47 . (canceled) 
     
     
         48 . A diagnostic instrument comprising:
 a reaction vessel holding a fluid sample to be analyzed by an assay;   a housing configured to receive the reaction vessel;   an optical unit disposed at least partly within the housing, the optical unit comprising:   an LED configured to provide an optical output for excitation of a prepared fluid sample within the reaction vessel;   an optical detector configured to detect reactions in the prepared sample in response to optical excitation within an assay; and   a control unit having a processor and a voltage sensor, the control unit configured to operate the LED to monitor performance of the assay, wherein the processor includes instructions recorded thereon configured for:   monitoring a voltage across the LED during operation at a given current;   correlating the voltage to a junction temperature of the LED such that the voltage is a proxy of the junction temperature;   determine a characteristic of the LED and/or photonic output based on the correlation.   
     
     
         49 . An opto-electronic system that maximizes signal-to-noise in its photodiode output, the system comprising;
 an LED-based excite block that illuminates a reaction-vessel, the excite block comprising:   an array of one or more LED;   a constant current LED driver that, upon command, drives current into a specified element of the LED array;   a voltage sensor that reads an LED voltage;   a temperature sensor that reads an excite block temperature;   a detect block that receives optical information from the illuminated sample, the detect block comprising:   an array of one or more photodiodes, each with a transimpedance amplifier to convert the photodiode current to a voltage;   a multiplexor to output a select photodiode voltage output;   a temperature sensor that measures an ambient temperature in a proximity of the reaction vessel;   a control unit operatively connected to the excite block, detect block and ambient sensor, wherein the control unit comprises a processor having instructions recorded thereon configured to:   determine a normalized and filtered photodiode output whereby the normalization and filtering compensates for an influence of a fluctuation of an LED power and/or an LED temperature on a noise variance of the photodiode signal during illumination of the sample.   
     
     
         50 - 51 . (canceled)